Membrane roofing is commonly used on flat or nearly flat roofs in North America, especially in commercial building structures with large roof surfaces, to prevent moisture penetration and move water off the roof. Common roof membrane materials include synthetic rubbers, thermoplastic plastics, asphalt, and modified bitumen. Roofing membranes can be custom-made to the precise sizes of the specific building roof surface in rolled transportable sheets, shipped to the construction site and then readily applied. The roofing membrane sheets can be made at a given width such as 10 feet (3 meters) or greater.
Compositions and membranes comprising thermoplastic olefin (TPO) polymers have recently found widespread use in the roofing industry for commercial buildings. TPO membranes are often fabricated as a composite structure including a reflective membrane (e.g., 1.0 to 1.5 millimeters thick) as an upper layer, a reinforcing polyester scrim fabric layer (e.g., 0.025 to 0.050 millimeter thick) as an intermediate layer, and a pigmented layer (e.g., 1.0 to 1.5 millimeters thick) as the lower layer. When the membrane is applied to the roof, the reflective upper layer is typically exposed to sunlight while the pigmented lower layer is attached to the roof insulation material.
During transport the rolls can be exposed to extreme heat conditions, such as from 40° C. to 100° C., which can lead to blocking of the rolls during installation. After installation, the membranes can be exposed during service to a wide range of conditions that may deteriorate or destroy the integrity of the membrane. As such, a membrane is desired that can withstand a wide variety of service temperatures, such as from −40° C. to 40° C.
PCT Application Publication No. WO 2010/115079A1 is directed to roofing membranes that contain compositions of Formula I that comprise (a) 30 to 50 wt % of a propylene-based elastomer, (b) 9 to 20 wt % of a plastomer, (c) from 7 to 20 wt % of an impact propylene-based elastomer, (d) 20 to 35 wt % of magnesium hydroxide, (e) 5 to 10 wt % of titanium dioxide, and (f) 1 to 2 wt % of additives; or compositions of Formula II that comprise (a) 32 to 48 wt % of a propylene-based elastomer, (b) 9 to 18 wt % of a plastomer, (c) 7 to 20 wt % of an impact propylene-based elastomer, (d) 25 to 35 wt % of magnesium hydroxide, (e) 4 to 6 wt % of titanium dioxide, (f) 0.75 to 1.5 wt % of UV inhibitor, (g) 0.2 to 0.45 wt % of antioxidant/stabilizer, (h) 0.15 to 0.4 wt % of thermal stabilizer, and (i) 0.1 to 0.2 wt % of lubricant. The propylene-based elastomer used in WO 2010/115079A1 was Vistamaxx™ 6102 Performance Polymer and the lubricant used was Asahi AX71 which is a mono or di-stearyl acid phosphate. The roofing membrane in WO 2010/115079A1 is formed around a scrim having reinforcing polyester threads.
PCT Application Publication No. WO 2014/001224A1 is directed to compositions comprising 40 to 75 wt % of at least one polypropylene-based elastomer and around 25 to 60 wt % of at least one random copolymer of polypropylene. The polypropylene-based elastomers used in WO 2014/001224A1 were Vistamaxx™ 3980, 6102, and 6202 Performance Polymers.
PCT Publication No. WO 2014/040914A1 is directed to thermoplastic mixtures that comprise at least one impact-resistant polypropylene copolymer and at least one ethylene-1-octene copolymer, where the weight ratio of impact-resistant polypropylene copolymer to ethylene-1-octene copolymer is in the range of 35:65 to 65:35.
U.S. Patent Application Serial No. 2010/0255739 A1 discloses roofing membrane with a composition having a polypropylene based elastomer, a plastomer, and an impact propylene-based elastomer. The total weight percent of propylene-based elastomer present in the composition may range from about 7 to 20 percent. It is disclosed therein that rolled sheets of such membrane can be supplied to the roofer and installed onsite using fasteners, adhesives and other means of fixation.
Additional background references include U.S. Patent Application Nos. 2006/0046084; 2007/208139; and 2010/197844; U.S. Pat. Nos. 6,743,864; 6,953,828; 6,750,284; 7,666,491; 7,927,595; and 8,769,903; and PCT Publication No. WO 2014/105809.
While such roofing membranes provide the workability for many applications, substitutes thereof with lower modulus at low temperature (e.g., temperature lower than −50° C.) and higher modulus at high temperature (e.g., temperature higher than 75° C.) are desired.